An electronic level gauge (ELG) utilizing radar is commonly used in industry as part of a guided-wave radar (GWR) or non-contact radar (NCR) system to measure the amount (e.g., level) of material (liquid or bulk solid (e.g., powder)) in a tank or a storage tank. An ELG provides continuous level (volume) measurement of high reliability at a generally reasonable price. The reliability is obtained due to lack of moving parts and insensitivity of the measurements to changes in process pressure, temperature, and density of measured material.
The ELG for GWR or NCR is mounted on top of the tank and measures the distance from a reference point, usually a mounting flange at the top of the antenna to the surface of the product material in the tank using reflection of the measuring signal from the surface of the product material. The product level value is obtained by subtracting the measured distance from a total height of the tank.
Tanks can include a variety of obstacles or obstructions in the path of the radar between the ELG and the surface of the measured material in the tank. For example, obstructions such as ladders, pipes or pumps may be mounted inside the tank. Because the obstructions can interfere with the radar signal reflected from the surface of the measured material in the tank, inaccurate level measurements can result. An obstruction is any internal non-product item in the tank or other object in the path of the measurement signal or close to the signal path of the measurement signal.